1. Field of the Invention
The present invention relates to a vacuum-heat-insulated utensil capable of maintaining temperature of foods after heated and cooked constant, while the foods are kept contained in the cooking utensil.
2. Related Art Statement
In recent years, various kinds of vacuum-heat-insulated cooking utensils such as a pan, cookpot, kettle and the like have been proposed which are capable of maintaining temperature of foods after heated and cooked constant, in such condition that the foods are contained in the cooking utensils, without the necessity of emptying of the cooking utensils into another heat-insulated container. Such a vacuum-heat-insulated cooking utensil generally comprises a container body having a double-walled, vacuum-heat-insulating side wall structure and a heat receiving bottom.
There is known a vacuum-heat-insulated cooking utensil of the type which is manufactured by connecting first ends of a pair of cylindrical side wall members to a disc-shaped metal plate or a heat receiving member and by connecting the other ends of the side wall members together with an annular member to thereby provide an annular space between the side wall members to be evacuated. There is also known a vacuum-heat-insulated cooking utensil of the type which is manufactured by connecting a separate tubular wall member to a side wall of a cup-shaped container to form, the double walled, heat-insulating side wall structure.
However, the above-described conventional vacuum-heat-insulated cooking utensil having the inner and outer side walls integrally connected to the bottom plate has suffered from such a disadvantage that in view of the complexity in construction, the manufacturing per se of such cooking utensil would become difficult and would increase the cost. On the other hand, the cooking utensil in which the separate wall member is connected to the side wall of the container has suffered from such disadvantages that the cooking utensil would be deteriorated in design, and the joint between the separate wall member and the side wall which is to be airtight would be complicated in structure and the welding of the joint would become troublesome.
As described above, the conventional vacuum-heat-insulated cooking utensils have the problem in construction or manufacturing manner and have not yet been put into practical use and it has been desired to solve the problems.